1. Technical Field
The present invention relates to a projector provided with two or more optical devices, and combining the light emitted from the respective optical devices to display an image.
2. Related Art
In the past, there has existed a projector provided with an optical device for separating the light emitted from a light source into three colored light of red (R), green (G), and blue (B), performing light modulation on the colored light using respective liquid crystal panels, and then combining the colored light, on which the light modulation has been performed, to emit it therefrom. Further, there has been known a projector provided with two such optical devices, and combining the light emitted from the respective optical devices to emit the combined light (see, e.g., JP-A-7-52262 (Document 1)).
The projector described in the Document 1 is a six-panel liquid crystal projector provided with two optical devices, each having three liquid crystal panels, combined with each other. The projector splits the light from the light source into S-polarized light and P-polarized light by polarization split, and leads the S-polarized light to one of the optical devices, and the P-polarized light to the other thereof. Then, each of the optical devices separates the polarized light thus input thereto into the colored light of R, G, and B, performs light modulation on the colored light using the respective liquid crystal panels, and combines the colored light, on which the light modulation has been performed, using a dichroic mirror, thereby generating image light with respect to the respective polarized light. Further, the image light combined by the respective optical devices are combined by the polarization split, and then emitted toward a projection object such as a screen.
Incidentally, in general, the color combining optical system such as a dichroic mirror of the projector reflects the red light and the blue light, and transmits the green light therethrough, thereby combining the colored light to form the image light. Therefore, it is possible to efficiently combine the colored light to form the image light by increasing the reflectance of the red light and the blue light with respect to the color combining optical system and increasing the transmission of the green light with respect to the color combining optical system, namely by using the S-polarized light with preferable reflectance as the red light and the blue light, and the P-polarized light with preferable transmission as the green light.
However, in the projector disclosed in the Document 1 described above, the polarization directions along which the respective colored light are combined with the dichroic mirror are not considered, and therefore, it is not achievable to appropriately combine the respective colored light to thereby form the image light. For example, in the optical device to which the S-polarized light is input, all of the colored light become the S-polarized light, and the light obtained by combining these colored light of the S-polarized light with each other provides poor transmission of the green light, which makes it quite difficult to form the preferable image light.
Incidentally, in order for solving the problem described above, it is also possible to adopt the configuration of changing the polarization directions of the light using a half-wave retardation plate before the light enter the color combining optical system to set the green light to be the P-polarized light, and the red light and the blue light to be the S-polarized light. However, in such a case, the light obtained by the combining operation of each of the optical devices becomes mixed light of the P-polarized light and the S-polarized light, and therefore, loss of light intensity is caused when combining the each image light with an optical component such as a polarizing beam splitter. In the case of the optical component such as the polarizing beam splitter used in the Document 1 described above, for example, the transmission of the P-polarized light increases, and the reflectance of the S-polarized light also increases. In the case of making the mixed light of the P-polarized light and the S-polarized light enter such an optical component, the light entering from the side facing straight to the projection direction has poor transmission of the S-polarized light, and the light entering from the side perpendicular to the projection direction has poor reflectance of the P-polarized light. In other words, the loss of light intensity is caused in the optical component, and the light efficiency is degraded.